Determination of appropriate radio resource to be requested in case of a circuit-switched (CS) fallback procedure

ABSTRACT

A system and method for implementing fallback on a wireless device for circuit switched fallback from a first network that does not provide a circuit switched domain service is presented. A paging message is received from the first network. The paging message instructs the wireless device to implement circuit switched fallback to a circuit switched network. The paging message is inspected for information indicative of a service associated with the paging message, and a channel type suitable for the service is determined from the information indicative of the service. A request message for initiating the establishment of a radio connection is transmitted. The request message identifies the suitable channel type, and the service is used on the circuit switched network.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 12/941,487,filed Nov. 8, 2010, which claims priority to European Patent ApplicationNo. 09306075.4 entitled “Determination of Appropriate Radio Resource tobe Requested in Case of a Circuit-Switched (CS) Fallback Procedure”,filed on Nov. 9, 2009, the applications are incorporated by reference.

BACKGROUND

The present disclosure relates generally to systems and methods forcommunications between a wireless device or user agent (UA) and anetwork and, more particularly, to systems and methods for coordinatingcommunications resources between wireless devices and networks includingcircuit switched networks.

As used herein, the term “user agent” or UA can refer to wirelessdevices such as mobile telephones, personal digital assistants (PDAs),handheld or laptop computers, and similar devices, including mobilestations (MS) or user equipment (UE) that have telecommunicationscapabilities. In some embodiments, a UA may refer to a mobile, wirelessdevice. The term “UA” may also refer to devices that have similarcapabilities but that are not generally transportable, such as desktopcomputers, set-top boxes, or network nodes.

A UA may operate in a wireless communication network that provideshigh-speed data and/or voice communications. The wireless communicationnetworks may implement circuit-switched (CS) and/or packet-switched (PS)communication protocols to provide various services. For example, the UAmay operate in accordance with one or more of an Enhanced UniversalTerrestrial Radio Access Network (E-UTRAN), Universal Terrestrial RadioAccess Network (UTRAN), Global System for Mobile Communications (GSM)network, Evolution-Data Optimized (EV-DO), Digital Enhanced CordlessTelecommunications (DECT), Digital AMPS (IS-136/TDMA), IntegratedDigital Enhanced Network (iDEN), Universal Mobile TelecommunicationsSystem (UMTS), Enhanced Data rates for GSM Evolution (EDGE), GPRS/EDGERadio Access Network (GERAN) and General Packet Radio Service (GPRS)technology. Other wireless networks that UAs may operate in include butare not limited to Code Division Multiple Access (CDMA), cdma2000,cdma2000 1xRTT, cdma2000 HRPD, WLAN (e.g. IEEE 802.11) and WRAN (e.g.IEEE 802.22). UAs may also operate in fixed network environments suchas, for example, Digital Subscriber Line (xDSL) environments, Data OverCable Service Interface Specification (DOCSIS) cable networks, WirelessPersonal Area Networks (PAN), Bluetooth, ZigBee, Wireless MetropolitanArea Networks (MAN) (e.g., WiMAX, IEEE 802.20, IEEE 802.22 Ethernet) oroptical networks. Some UAs may be capable of multimode operation wherethey can operate on more than one access network technology either on asingle access network at a time or in some devices using multiple accesstechnologies simultaneously.

In wireless telecommunications systems, transmission equipment in a basestation transmits signals throughout a geographical region known as acell. As technology has evolved, more advanced equipment has beenintroduced that can provide services that were not possible previously.This advanced equipment might include, for example, an evolved universalterrestrial radio access network (E-UTRAN) Node B (eNB) rather than abase station or other systems and devices that are more highly evolvedthan the equivalent equipment in a traditional wirelesstelecommunications system. Such advanced or next generation equipmentmay be referred to herein as long-term evolution (LTE) equipment, and apacket-based network that uses such equipment can be referred to as anevolved packet system (EPS). As used herein, the term “access device”will refer to any component, such as a traditional base station, eNB, orother LTE access device, that can provide a UA with access to othercomponents in a telecommunications system.

The different networks described above provide varying services toconnected UAs. Some networks, for example, provide only PS services andcannot provide CS voice or other CS domain services. As such, a UA maybe configured to connect to multiple network-types to access both PS andCS domain services. For example, if a UA is connected to a first networkcell that does not provide CS domain services, the UA may be configuredto implement a CS fallback procedure, which may be referred to herein as“CS fallback”, to connect to an accessible network such as a GERAN orUniversal Terrestrial Radio Access Network (UTRAN) to access the voiceor other CS domain services provided by those networks. As such, the CSfallback procedure allows a UA connected to a network using a firstradio access technology (RAT) and that provides only PS domain services,to connect to another network that provides CS domain services. CSfallback may be used, for example, to initiate voice calls via a cell ofa network providing CS domain services, when, at the time of initiatingthe voice call, the UA was associated to a cell of a network that onlyprovides PS domain services. The UA initiating the voice call may beeither idle or connected (e.g., active) on the cell of the network thatonly provides PS domain services. In case the UA is idle, it can be saidto be camped on the cell and may be monitoring the paging channel ofthat cell for paging messages for mobile terminated sessions or calls.In case the UA is connected, it may be communicating with the cell andtransferring data for a PS domain service.

Turning to FIG. 1, an example CS fallback process is illustrated wherebya UA 10 transitions from an E-UTRAN network cell 12 to a GERAN or UTRANcell 14 to access CS domain services for initiating a voice call. Aswill be described, to facilitate CS fallback, the UA 10 may beconfigured to communicate with both PS-based and CS-based networks. Forexample, the UA 10 may support combined procedures for EPS/InternationalMobile Subscriber Identity (IMSI) attach, and Tracking Area update forregistering with a Mobility Management Entity (MME) to access PS domainservices (for example, via an E-UTRAN, UTRAN or GERAN access network)and for registering with a Mobile Switching Center (MSC) to access CSdomain services (for example, via a UTRAN or GERAN access network oranother network supporting CS domain services). The combined proceduresalso allow the MSC and MME to create an association between one anotherso that each is aware that the UA 10 is simultaneously registered withboth the MSC and MME and that, therefore, the UA 10 is registered withboth the PS and CS network.

FIG. 2 is a data flow diagram illustrating an example data flow for amobile-terminated CS fallback procedure where the UA 10 in connectedmode is redirected to GERAN or UTRAN. In FIG. 1, the UA 10 is initiallyconnected to E-UTRAN cell 12. Because E-UTRAN cell 12 does not provideCS domain services, UA 10 implements CS fallback to communicate with theGERAN or UTRAN cell 14 to access CS domain services provided thereby.

By way of example, a network assisted cell change (NACC) related to amobile originated voice call will be described. Referring to FIGS. 1 and2, the example process begins by a MSC 16 sending a CS paging 18 to aMME 20, which in turn prompts the MME 20 to send a CS servicenotification paging 22 to the UA 10. In FIG. 1 communications from theE-UTRAN cell 12 are indicated by arrow 23 and communications from the UA10 to the E-UTRAN cell 12 are indicated by arrow 25. Responsive to theCS service notification paging 22, the UA 10 sends an Extended servicerequest 24 to the eNB 26 of the E-UTRAN cell 12. However, the E-UTRANcell is not configured to provide CS domain services. Thus, the MME 20sends a S1 application protocol (S1-AP) message with a CS fallbackindicator 30 to the eNB 26.

To streamline the exemplary data flow, FIG. 2 indicates some data flowsby boxes, such as optional measurement report 32 which may be providedby the UA 10 to indicate information, such as signal strength and thelike of neighboring cells to which it may be assigned. That is, whenperforming CS fallback, the UA 10 may be in the best position todetermine which cell or cells are candidate cells to which to fallback.As such, the UA 10 can detect which cells are in close proximity or haveparticularly strong received signal strength or quality (or other suchparameters), and hence with which cells the UA 10 would likely have asuccessful connection following the CS fallback process. Accordingly,during the CS fallback process, the UA 10 may undertake a measurementstep to detect and identify the cells accessible to the UA 10. In otherwords, before falling back to a cell providing CS domain services, theUA 10 may search for available candidate network cells via a measurementprocess.

The eNodeB (eNB) may trigger an inter-RAT cell change order, optionallywith NACC signal 34 that is sent to the UA 10, alternatively aconnection release with redirection is signaled 36. The eNB 26indicates, according to S1-AP, a UA context release request 38 to theMME 20. Thereafter, the S1 UA context release 40 takes place, a locationarea (LA) update, a combined routing area (RA)/LA update, a RA update,or a LA update and RA update 42 occurs in the new GERAN or UTRAN cell.If the target RAT is GERAN, a suspension of PS services may take placeif the new cell or the UA does not support concurrent CS and PSservices. In this case, a suspend message 44 is sent from the UA 10 to abase station system (BSS) 46, which is then communicated from the BSS 46to a serving GPRS (general packet radio service) Support Node (SGSN) 48.Thereafter, a suspend request/response 50 is communicated between theSGSN 48 and MME 20 and an update of bearer(s) 52 takes place between theMME 20 and a serving gateway (S-GW) 54.

The UA 10 signals a paging response 56 to the BSS/RNS 46, which in turnforwards this paging response to the MSC 16. If the CS fallback entailsa change of the MSC 16, additional steps may be carried out, asindicated in box 58, such as communicating a connection rejection 60from the MSC 16 to the BSS/RNS 46, communicating a connection release 62from the BSS/RNS 46 to the UA 10, and an LA update or combined RA/LAupdate 64. Finally, a CS call establishment procedure 66 occurs, suchthat, as indicated in FIG. 1, the UA 10 can move, as indicated by arrow68, from communicating with the E-UTRAN cell 12 to communicate, asindicated by arrow 70, with the GERAN or UTRAN cell 14 over a CSchannel.

When implementing CS fallback, delay may be a concern. If the UA 10 isinitially camped on E-UTRAN cell 12 and wishes to access CS domainservices in the GERAN or UTRAN Cell 14, a CS fallback process may beexecuted. While a radio resource control (RRC) connection setupprocedure of the CS fallback process may be relatively short (e.g.,about 150 ms is the target time for the E-UTRA system design),measurement steps and a step for selecting the target cell for CS domainservices can potentially take a significant amount of time. As such, CSfallback may be delayed resulting in delays in establishing the CSdomain services, possibly delaying the establishment of a connection forthe user or negatively affecting other services accessed by the UA 10.

In addition to this potential for a user experiencing a perceivabledelay in services, CS fallback can result in inefficient orinappropriate uses of network resources. For example, when a UA is pagedin a GERAN or UTRAN network for a mobile-terminating call, someinformation is communicated by the network in the paging message. Thatis, the paging message may provide an indication of the service forwhich the UA is paged, or an indication of the appropriate radio channeltype for supporting the service. Similarly, in case of amobile-originating (MO) call, the UA is indicating to the network anestablishment cause reflecting the service or the channel typerequested. Thus, the network can reasonably allocate channelsappropriate for the desired communication.

However, such information either is not available on the correspondingE-UTRAN interfaces used when initiating the CS fallback procedure, or isavailable but is not assessed for requesting/allocating the radiochannels in GERAN, UTRAN or E-UTRAN. As a consequence, the network maydecide to allocate non-optimal resources, such as a signaling channelfor serving a voice call, which can affect the CS fallback performance,or a traffic channel for serving a signaling procedure, causing a wasteof the radio resource.

Thus, systems and methods that address the above-listed issues and allowthe setting and the usage of optimal resources for CS fallback wouldprovide a useful improvement in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, like reference numerals represent likeparts or operations.

FIG. 1 is an illustration of an example CS fallback process wherein a UEtransitions from an E-UTRAN cell to a GERAN or UTRAN cell to access CSdomain services for initiating a voice call;

FIG. 2 is a data flow diagram illustrating an example data flow for aMobile Terminating CS fallback procedure where a UA in connected mode isredirected to GERAN or UTRAN without PS Handover;

FIG. 3 is a data flow diagram illustrating an example Mobile Terminatingcall initiation in a GERAN network wherein the UA is in idle mode;

FIG. 4 is a data flow diagram illustrating an example Mobile Terminatingcall initiation in a UTRAN network wherein the UA is in idle mode;

FIG. 5 is a data flow diagram illustrating an example Mobile OriginatingCS fallback procedure with Packet Switched Handover initiated in anE-UTRAN network;

FIG. 6 is an illustration of data flow for implementing an exampleMobile Terminating CS fallback where service related information ispassed to the UA in idle mode within a paging message;

FIG. 7 shows a block diagram of the user equipment (UA);

FIG. 8 illustrates a software environment that may be implemented by aprocessor of a user equipment; and

FIG. 9 illustrates an example of a system that includes a processingcomponent suitable for implementing a method for providing continuityfor sessions transitioning between networks.

DETAILED DESCRIPTION

The present disclosure provides a system and method for circuit-switched(CS) fallback and, specifically, for minimizing delay, optimizing radioresource allocation and improving reliability for CS fallback.

One embodiment of the invention includes a method for implementingfallback on a wireless device for circuit switched fallback from a firstnetwork that does not provide a circuit switched domain service. Themethod includes receiving a paging message from the first network. Thepaging message instructs the wireless device to implement circuitswitched fallback to a circuit switched network. The method includesinspecting the paging message for information indicative of a serviceassociated with the paging message, determining from the informationindicative of the service a channel type suitable for the service, andtransmitting a request message for initiating the establishment of aradio connection. The request message identifies the suitable channeltype. The method includes using the service on the circuit switchednetwork.

Other embodiments include a wireless device configured to performcircuit switched fallback from a first network that does not provide acircuit switched domain service including a processor configured toconstruct a service request message. The service request messageidentifies a cause for a circuit-switched (CS) service to be provided bya circuit switched network. The processor is configured to transmit theservice request message to the first network. The service requestmessage initiates a fallback procedure. The processor is configured toestablish a connection to the circuit switched network, and use the CSservice on the circuit switched network.

Other embodiments include a wireless device configured to performcircuit switched fallback from a first network that does not provide acircuit switched domain service including a processor configured toreceive a paging message from the first network. The paging messageinstructs the wireless device to implement circuit switched fallback toa circuit switched network. The processor is configured to inspect thepaging message for information indicative of a service associated withthe paging message, determine from the information indicative of theservice a channel type suitable for the service, and transmit a requestmessage for initiating the establishment of a radio connection. Therequest message identifies the suitable channel type. The processor isconfigured to use the service on the circuit switched network.

The various aspects of the disclosure are now described with referenceto the annexed drawings, wherein like numerals refer to like orcorresponding elements throughout. It should be understood, however,that the drawings and detailed description relating thereto are notintended to limit the claimed subject matter to the particular formdisclosed. Rather, the intention is to cover all modifications,equivalents, and alternatives falling within the spirit and scope of theclaimed subject matter.

As used herein, the terms “component,” “system,” and the like areintended to refer to a computer-related entity, either hardware, acombination of hardware and software, software, or software inexecution. For example, a component may be, but is not limited to being,a process running on a processor, a processor, an object, an executable,a thread of execution, a program, and/or a computer. By way ofillustration, both an application running on a computer and the computercan be a component. One or more components may reside within a processand/or thread of execution and a component may be localized on onecomputer and/or distributed between two or more computers.

The word “exemplary” is used herein to mean serving as an example,instance, or illustration. Any aspect or design described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other aspects or designs.

Furthermore, the disclosed subject matter may be implemented as asystem, method, apparatus, or article of manufacture using standardprogramming and/or engineering techniques to produce software, firmware,hardware, or any combination thereof to control a computer or processorbased device to implement aspects detailed herein. The term “article ofmanufacture” (or alternatively, “computer program product”) as usedherein is intended to encompass a computer program accessible from anycomputer-readable device, carrier, or media. For example, computerreadable media can include but are not limited to magnetic storagedevices (for example, hard disk, floppy disk, magnetic strips, and thelike), optical disks (for example, compact disk (CD), digital versatiledisk (DVD), and the like), smart cards, and flash memory devices (forexample, card, stick, and the like). Additionally, it should beappreciated that a carrier wave can be employed to carrycomputer-readable electronic data such as those used in transmitting andreceiving electronic mail or in accessing a network such as the Internetor a local area network (LAN). Of course, those skilled in the art willrecognize many modifications may be made to this configuration withoutdeparting from the scope or spirit of the claimed subject matter.

As addressed above, there is the potential for CS fallback to cause theallocation of non-optimal resources such as a signaling channel forserving a voice call, which can create situations that affect the CSfallback performance, or a traffic channel for serving a signalingprocedure, causing a waste of radio resources. For example, turning toFIG. 3, in the case of a Mobile Terminating call initiation in GERAN,the UA 10 is typically provided with the “Channel Needed” indication ina paging message 72 sent by the GERAN network 74, which is informationthat signals the more suitable radio channel for supporting the servicefor which the UA is paged, for example, Stand-Alone Dedicated ControlChannel (SDCCH) signaling channel, traffic channel (TCH)/full(F). The UA10 then sends an appropriate channel request 76 to the GERAN network 74taking into account the “Paging indication” of the “Channel Needed”element received in the paging message 72 and the UA's 10 own capability(full rate only, dual rate, SDCCH only), which allows the BSS to grantthe most desirable channel. For example, Table 1 below lists the channelrequest messages when answering a paging for RR connectionestablishment.

TABLE 1 MS Capability Paging SDCCH Indication Full rate only Dual rateonly Any channel 100xxxxx 100xxxxx 100xxxxx SDCCH 0001xxxx 0001xxxx0001xxxx TCH/F 100xxxxx 0010xxxx 0001xxxx TCH/H or TCH/F 100xxxxx0011xxxx 0001xxxx

However, in the case of paging a UA in E-UTRAN for a CS fallbackterminating session, the paging (CS service notification) sent by theMME 20, as described with respect to FIG. 2, to the UA 10 in connectedmode in the source (packet only) network does not contain any “PagingIndication” information. This paging notification may includeinformation about the service for which the mobile station is paged(e.g. Supplementary Service code, location service (LCS) indicator). Incase the paging is made for reaching a UA 10 in Idle mode, (see, forexample, FIG. 6), the paging messages sent over the S1 interface andover the radio interface do not even contain any indication of theservice for which the mobile station is paged. Furthermore, the GERAN RRprotocol does not specify how the UA should build the Channel Requestwhen answering the page when triggered by the CS fallback procedure.This means that the existing channel request procedure defined for GERANis not applicable as such for CS fallback (lack of “Paging Indication”)for determining the proper and optimal information in channel requestmessage that may be sent in the target network.

As a result, a CS fallback to GERAN could lead to inconsistent UAimplementations, for example, requesting for a channel typeinappropriate to the service being activated, resulting in the waste ofthe resources allocated or a longer establishment time. In particular,the request and initial allocation of a SDCCH in case of a voice callsetup will delay the voice path establishment compared with the casewhere a traffic channel (TCH) is requested and allocated in signalingonly mode (higher latency of SDCCH compared to TCH, longer time forassigning the TCH in speech mode if a SDCCH has been allocated comparedto a channel mode modification procedure while staying on the same TCHchannel). In other scenarios, the request and initial allocation of aTCH in signaling only mode would waste radio resource if the service,for example, location service or supplementary service, can be supportedon a SDCCH.

Turning to another exemplary identified problem, FIG. 4, illustrates amobile-terminating CS call in UTRAN network 78, with the UA 10 in idlemode. In this case, the UA 10 is typically provided with a “pagingcause” information in the paging message sent by the UTRAN network 78,which is information that signals the type of service for which the UAis paged, for example, Terminating Conversational Call, Terminating HighPriority Signaling, Terminating Low Priority Signaling, as indicated by“paging type 1” 80. This information is forwarded by the RRC protocol inthe UA 10 to the upper layers, which in turn request the establishmentof the RRC connection and map the RRC establishment cause to thereceived paging cause, which will be included in the RRC ConnectionRequest 82 sent to the UTRAN network 78.

However in the case of paging a UA in E-UTRAN for a CS fallbackterminating session, the paging (CS service notification) sent by theMME to the UA in connected mode in the source, packet only (e.g., PS),network does not contain any “paging cause” information. This pagingnotification may include information about the service for which themobile station is paged.

In case the paging is made for reaching a UA in Idle mode, the pagingmessage sent over the S1 interface and over the radio interface does notcontain any indication of the service for which the UA is paged.Furthermore, the higher layers do not specify which information shouldbe passed to the RRC protocol for inclusion in the RRC ConnectionRequest in response to a paging having taken place in E-UTRAN for thecase of the CS fallback procedure. Again, in UTRAN, this could lead toinconsistent UA implementations and result in significantly sub-optimalresource allocations or performances.

In the case of a mobile-originating call in GERAN or in UTRAN, the UAincludes in the channel request/RRC Connection Request sent to thenetwork some additional information, such as channel type, establishmentcause, and the like, allowing the network to allocate appropriateresource depending on the service which is requested. Turning now toFIG. 5, which is a variation on FIG. 2 but showing a dataflow for amobile-originated call subject to CS fallback, the data flow includesoperation 24 for handling a service request from the UA 10 to thenetwork. The service type information element is included in theExtended Service Request message sent to the network. The service typeinformation elements are as follows in Table 2:

TABLE 2 Service type value (octet 1) Service type value Bits 4 3 2 1 0 00 0 mobile originating CS fallback or 1xCS fallback 0 0 0 1 mobileterminating CS fallback or 1xCS fallback 0 0 1 0 mobile originating CSfallback emergency call or 1xCS fallback emergency call All other valuesare reserved.

However, this information element does not provide any information tothe source network on the CS service requested, which, thus, does notallow the network to properly dimension the resources to be allocatedaccording to the requested service and to determine optimal conditionsfor handing over the UA to the target CS network, for example, dependingon available channels and load information, for the case inter-RAThandover or cell change order is supported.

In general, the present system and methods have been developed to reducethe delay and improve the reliability of a CS fallback process. CSfallback may be implemented for transitioning from E-UTRAN to GERAN,specifically, or, more generally, from a first network that does notprovide CS domain services to a second network that does provide CSdomain services. For example, CS fallback may be implemented to allowfallback from E-UTRAN networks to GERAN, UTRAN or CDMA2000 networks. Tothis end, the present system and method facilitates CS fallback byallowing a UA to identify the most appropriate resources for providingthe requested service and then request those resources whentransitioning to a CS network during CS fallback. In one implementationof the present system, the UA is configured to analyze available paginginformation received from the network to determine the most appropriatecommunication channel or radio resource to request for optimal CSfallback performance.

To initiate CS fallback, a UA may first receive a paging message from asource PS network (e.g., an E-UTRAN network). The paging messageinstructs the UA to implement CS fallback to a CS network (e.g., a GERANnetwork) to access a service. If the related service can be determinedusing the information conveyed in the paging message, the UA isconfigured to send a channel request message requesting a channel typesuitable for that service on the CS network. As such, based upon one ormore pieces of information contained in the paging message, the UA isconfigured to request particular channel types when implementing CSfallback.

For example, when the paging message is for a speech call or for anycall requiring a traffic channel, the UA may be configured to request a“TCH/H or TCH/F”, or else a “TCH/F” channel. Alternatively, when thepaging message is for activating a call independent supplementaryservice, or a location service, for example, the UA may request a SDCCH.In these examples, the selection of a “TCH/H or TCH/F” channel may notrequire any particular preference for the selection of a half rate (H)or a full rate (F) channel. The network may make the determination of afull or half-rate channel autonomously depending on local conditions(network load status, quality of service (QoS) preferences, etc.). Theselection of a TCH/F channel, however, may influence the networkdecision of whether to select a full or half-rate channel.

In some circumstances, the paging message will contain insufficientinformation for the UA to determine the service for which the UA ispaged. In that case, the UA may be configured to build and send achannel request reflecting a “default” channel type, e.g. using thevalue “Any Channel” or some other indicator that identifies the defaultchannel.

Accordingly, in one example implementation of the present system, in thecase of a CHANNEL REQUEST triggered by a CS fallback procedure, such asthat described in 3GPP TS 23.272, the CHANNEL REQUEST message contentmay be determined depending on the information that can be derived fromthe paging notification received in the source radio access technology(RAT) about the service for which the mobile station is paged. If nospecific information can be derived from the paging notification, theCHANNEL REQUEST message content may be set as for a Paging Indicationvalue indicating “Any channel”. For example, the CHANNEL REQUEST messagecontent may be encoded in accordance with Table 3, with the “PagingIndication” entry selected according to the description above toindicate the related service.

TABLE 3 MS Capability Paging Indication Dual rate SDCCH (note 3) Fullrate only (note 5) only Any channel 100xxxxx 100xxxxx 100xxxxx SDCCH0001xxxx 0001xxxx 0001xxxx TCH/F 100xxxxx 0010xxxx 0001xxxx TCH/H orTCH/F 100xxxxx 0011xxxx 0001xxxx

Alternatively, the UA may be configured to select a channel of “TCH/H orTCH/F”, or SDCCH, depending on whether fast establishment or radioresource saving is preferred (the preference may be stored as userpreferences, or determined by the network operator policy, for example),or some other factor that may require a particular default channel.

Depending upon the system implementation, the UA may be configured withan explicit mapping between the service indicated by the paging messageand a channel type to be requested during fallback. In other cases,however, after determining the service indicated in the paging message,the UA may determine the channel type to request independently basedupon other information available to the UA. If there is no explicitmapping, and the UA can independently determine the channel type to berequested, the UA may have more flexibility and may rely on other piecesof available information when identifying the channel type to request.In contrast, an explicit mapping may preclude different interpretationsand ensure consistency in the channel selected by a UA in response to aparticular paging message.

In one example of the present system, various information elementspresent in a CS Service Notification message transmitted between the MMEand the UA may be inspected to determine the service for which the UA ispaged and may, therefore, allow the UA to request the most appropriatechannel type for providing that service. The calling line (CLI),supplementary service (SS) Code, LCS indicator, and LCS client identityinformation elements, for example, may be included within a CS ServiceNotification Message and their presence or absence can be indicative ofthe service being requested. Generally, the CLI contains theidentification of the calling line for the mobile terminating call inthe CS domain that triggered the paging via SGs. The SS Code informationelement contains information on the supplementary service transaction inthe CS domain that triggered the paging via SGs. The LCS indicatorindicates that the paging was triggered by a terminating LCS request inthe CS domain. The LCS client identity contains information related tothe requestor of the terminating LCS request in the CS domain. Each ofthe information elements are sent by the network if they are originallyreceived via SGs. Table 4 illustrates a CS SERVICE NOTIFICATION messagecontent.

TABLE 4 Information IEI Element Type/Reference Presence Format LengthProtocol Protocol M V ½ discriminator discriminator 9.2 Security headerSecurity header M V ½ type type 9.3.1 CS service Message type M V 1notification 9.8 message identity Paging identity Paging identity M V 19.9.3.25A 60 CLI CLI O TLV 3-14  9.9.3.38 61 SS Code SS Code O TV 29.9.3.39 62 LCS indicator LCS indicator O TV 2 9.9.3.40 63 LCS clientLCS client O TLV 3-257 identity identity 9.9.3.41

These information elements may be originally received from theMSC/Visitor Location Register (VLR) in a SGsAP-PAGING-REQUEST messageand passed along in the CS SERVICE NOTIFICATION message. The presence orabsence of the information elements in the SGsAP-PAGING-REQUEST messageis governed by various rulesets and is indicative of the type of servicefor which CS fallback is requested. For example, if the paging is due toa network-initiated Call Independent SS procedure as defined in 3GPP TS24.010, the VLR includes the SS code in the SGsAP-PAGING-REQUEST messageas defined in 3GPP TS 29.002. If, however, the paging is due to a MobileTerminated Location Request as defined in 3GPP TS 24.030, the VLR mayinclude the LCS client identity and LCS indicator as defined in 3GPP TS29.002 in the SGsAP-PAGING-REQUEST. In accordance with these rules, thevarious information elements are included in the SGsAP-PAGING-REQUESTand are forwarded to the UA in the CS SERVICE NOTIFICATION messagecontent. As such, the presence or the absence of one or several of theseinformation elements allows the UA to make a determination of theservice for which the UA is paged.

Table 5 illustrates an example SGsAP-PAGING_REQUEST message content.

TABLE 5 Information element Type/Reference Presence Format LengthMessage type Message type M V 1 9.2 IMSI IMSI M TLV 6-10 9.4.6 VLR nameVLR name M TLV 3-n 9.4.22 Service indicator Service indicator M TLV 39.4.17 TMSI TMSI O TLV 6 9.4.20 CLI CLI O TLV 3-14 9.4.1 Location areaLocation area O TLV 7 identifier identifier 9.4.11 Global CN-Id GlobalCN-Id O TLV 7 9.4.4 SS code SS code O TLV 3 9.4.19 LCS indicator LCSindicator O TLV 3 9.4.10 LCS client identity LCS client identity O TLV3-n 9.4.9 Channel needed Channel needed O TLV 3 9.4.23 eMLPP PriorityeMLPP Priority O TLV 3 9.4.24

As shown in Table 5, the SS code is included if paging is due to anetwork-initiated Call Independent SS procedure (see 3GPP TS 24.010).The LCS indicator is included if the paging is due to a MobileTerminated Location Request (see 3GPP TS 24.030). The LCS clientidentity is included if the paging is due to a Mobile TerminatedLocation Request (see 3GPP TS 24.030). The Channel needed informationelement is included if the VLR intends to indicate which channel the UAshould use.

The UA may be further configured to inspect additional information todetermine the services indicated by a particular paging request. Theadditional information may include other information elements that canbe added in the future, including those identified below.

The present system may also be configured to include service relatedinformation available at the MME in paging messages used to page a UA inidle mode. For example, service related information may be added to S1and RRC paging messages. In one example, the service related informationmay include the “SS Code”, “LCS indicator”, and “LCS client identity”information elements described above. The service related informationmay be communicated to the MME by the MSC/VLR over the SGs interface inthe SGsAP-PAGING-REQUEST message. In some cases, these informationelements are already present in the CS Service Notification message usedto page a UA in connected mode and may, therefore, be added to the S1interface Paging message by the MME and to the E-UTRAN RRC radiointerface Paging message by the E-UTRAN RRC protocol. The additionalinformation presented in the paging messages may then be used when theUA is paged in idle mode in addition to the case where the UA is pagedin connected mode.

Table 6 illustrates an S1 interface paging message that is modified toinclude the SS Code, LCS indicator, and LCS client identity informationelements.

TABLE 6 IE type and Semantics Assigned IE/Group Name Presence Rangereference description Criticality Criticality Message Type M 9.2.1.1 YESignore UE Identity Index value M 9.2.3.10 YES ignore UE Paging IdentityM 9.2.3.13 YES ignore Paging DRX O 9.2.1.16 YES ignore CN Domain M9.2.3.22 YES ignore List of TAIs M YES ignore >TAI List Item 1 to EACHignore <maxnoofTAIs> >>TAI M 9.2.3.16 — CSG Id List 0 to GLOBAL ignore<maxnoofCSGId> >CSG Id M 9.2.1.62 SS Code O 9.2.x.y — LCS indicator O9.2.x.y — LCS client identity O 9.2.x.y —

Table 7 illustrates an E-UTRAN RRC protocol paging message that ismodified to include the SS Code, LCS indicator, and LCS client identityinformation elements.

TABLE 7 -- ASN1START Paging ::=      SEQUENCE {   pagingRecordList  PagingRecordList   OPTIONAL, -- Need ON   systemInfoModification    ENUMERATED {true}   OPTIONAL, -- Need ON   etws-Indication    ENUMERATED {true}   OPTIONAL, -- Need ON   nonCriticalExtension  SEQUENCE { }   OPTIONAL -- Need OP } PagingRecordList ::= SEQUENCE(SIZE (1. . . maxPageRec)) OF PagingRecord PagingRecord ::= SEQUENCE {  ue-Identity   PagingUA-Identity,   cn-Domain     ENUMERATED {ps, cs},  . . .   ss-Code     OCTET STRING (SIZE(1)),   Ics-Indicator   OCTETSTRING (SIZE(1)),   Ics-Client-Identity   OCTET STRING (SIZE(1. . .255))   . . . } PagingUA-Identity ::= CHOICE {   s-TMSI     S-TMSI,  imsi   IMSI,   . . . } IMSI ::= SEQUENCE (SIZE (6. . . 21)) OFIMSI-Digit IMSI-Digit::= INTEGER (0. . . 9) -- ASN1STOP

Referring to Table 7, the ss-Code conveys information related to anetwork initiated supplementary service request. The Ics-Indicatorindicates that the origin of the message is due to a LCS request and thetype of this request. The coding of the Ics-Indicator is given by thevalue part of the LCS indicator information element in TS 24.301. TheIcs-Client-Identity conveys information related to the client of a LCSrequest. The coding of the LCS client identity is given in subclause17.7.13 of 3GPP TS 29.002.

FIG. 6 is an illustration of a message flow for implementing CS fallbackwhere service related information is passed to UA 10 within a pagingmessage. In steps 100, 102, and 104 a UA-terminated call arrives at theMSC/VLR 140. In step 106, a SGsAP-Paging-Request message is transmittedto the MME 20. The SGsAP-Paging-Request may include one or moreinformation elements indicative of the service type requested. In steps108 and 110 the MME 20 forwards a paging message to the UA 10. Thepaging message is modified to include one or more of the informationelements described above. The presence or absence of one or more of theinformation elements allows the UA to identify the service type forwhich the paging message is sent. As a result, in step 112 the UA canrequest an appropriate resource for the service. In step 114, inresponse to the service request, the MME 20 issues an initial UA contextsetup message. In step 116, 118 and 120 a PS handover or, alternatively,a base station assisted cell change, or a RRC release with redirection,possibly followed by a location area update are completed. In step 122the paging response is transmitted to the RNC/BSC 142 from the UA 10 andthe paging response is forwarded to the MSC/VLR 140 in step 124. If theMSC is not changed, the CS connection is established in step 126 and theCS fallback process is completed. If the MSC is changed, however, instep 128 the MSC/VLR 140 transmits a connection rejection to the RNC/BSC142. In response, the RNC/BSC 142 transmits a signaling connectionrelease to the UA 10 in step 130. At that point, a location area updateand roaming retry is initiated to against attempt CS fallback in step132.

Alternatively, to facilitate CS fallback, a Channel Needed informationelement, when know to the MME, may be added to Paging messages sent to aUA to page the UA in idle or connected mode. For example, a ChannelNeeded information element may be added to the CS Service NotificationNAS message (described above) transmitted between the MME and the UA,the S1 interface Paging message described above, or the RRC radiointerface protocol described above. In some cases, the data used topopulate the Channel Needed information element is communicated to theMME by the MSC/VLR over the SGs interface in the SGsAP-PAGING-REQUESTmessage, as described above. The Channel Needed information, whenpresent within a paging message, allows the UA to efficiently create anappropriate channel request message when the UA answers the CS fallbackpage in GERAN, as the same information would be present as in the GERANpaging message (if transmitted by the MSC/VLR).

For enabling the UA paged in E-UTRAN for a Mobile Terminating CS callwith fallback to send an appropriate establishment cause when answeringin an UTRAN network, new mapping entries may be introduced. This wouldallow the UA to communicate to the network the appropriate establishmentcauses reflecting the service for which the UA is paged, if the relatedservice can be assessed from the information conveyed in the pagingmessage. In that case, the UA, when answering in UTRAN to a pagereceived in the source packet network (e.g. E-UTRAN), may include themapped establishment cause communicated by the upper layers in the RRCConnection Request message.

As an example, the establishment cause may be determined as follows: Theestablishment cause may be “Terminating Conversational Call” when thereceived page is for a speech call or for any other conversational CScall, or “Terminating High Priority Signalling” when the received pageis for activating a call independent supplementary service, or alocation service.

If the service for which the UA is paged cannot be assessed from theinformation available from the network, the UA may use“Terminating—cause unknown” as the establishment cause.

Table 8 illustrates an exemplary mapping of CS NAS procedure toestablishment cause.

TABLE 8 RRC Establishment cause (according 3GPP TS CS NAS procedure25.331 [23c]) Originating CS speech Originating Conversational Call callOriginating CS data call Originating Conversational Call CS Emergencycall Emergency call Call re-establishment Call re-establishment Locationupdate Registration IMSI Detach Detach MO SMS via CS domain OriginatingLow Priority Signalling Supplementary Services Originating High PrioritySignalling Answer to circuit Set equal to the value of the paging causeused switched paging in the reception of paging in the RRC layer SS partof Location Originating High Priority Signalling services Answer tocircuit switched paging in case of Terminating CS fallback: TerminatingCS Terminating Conversational Call speech/data call SupplementaryTerminating High Priority Signalling Services Location ServicesTerminating High Priority Signalling Not determined Terminating - causeunknown

Various information elements, when present in a CS Service Notificationmessage between the MME and the UA, may provide an indication of theservice for which the mobile is paged, including the “SS Code”, “LCSindicator”, and “LCS client identity” information elements. The variousinformation elements may be received from the MSC/VLR in aSGsAP-PAGING-REQUEST message as described above. The presence or theabsence of one or several of these information elements may thereforeallow the UA to make a determination of the service for which the UA ispaged. Any other information that could be accessed or retrieved by theUA from messages received from the network or other sources may be usedto determine the service for which the UA is paged. This may include newinformation elements added in the future, including those describedabove.

When initiating a Mobile Originating (MO) call, the UA may be configuredto provision additional information to the PS network describing therequested CS service for which CS fallback may be triggered. In oneimplementation, the UA includes additional information in the ExtendedService Request message transmitted to the MME of the PS networkdescribing the CS service being requested. Similarly, the additionalinformation may be included in an INITIAL CONTEXT SETUP REQUEST, or UACONTEXT MODIFICATION REQUEST messages transmitted from the MME to theeNodeB using the S1 interface (see 3GPP TS 36.413).

Table 9 and Table 10 illustrate a modified Extended Service Requestmessage including additional information describing the CS servicerequested by a UA initiating a MO call resulting in CS fallback.

TABLE 9 Information IEI Element Type/Reference Presence Format LengthProtocol Protocol M V ½ discriminator discriminator 9.2 Security headerSecurity header M V ½ type type 9.3.1 Extended service Message type M V1 request message 9.8 identity Service type Service type M V ½ 9.9.3.27NAS key set NAS key set M V ½ identifier identifier 9.9.3.21 M-TMSIMobile identity M LV 6 9.9.2.3 B- CSFB response CSFB response C TV 19.9.3.5 C- Extended service Extended service C TV 1 request causerequest cause 9.9.x.y

TABLE 10 8 7 6 5 4 3 2 1 Extended service 0 Extended service octet 1request cause spare request cause IEI value

As shown in Table 9 and Table 10, the Extended Service Request messageshown in Table 9 includes an additional element called “Extended servicerequest cause”. The detail of the Extended service request causeinformation element is shown in Table 10. The Extended service requestcause element is configured to store an identifier value in octet 1 thatdescribes the requested CS service. For example, the identifier may beused to refer to CS services such as Originating Conversational Call,Originating High Priority Signalling, or Originating Low PrioritySignalling. Table 11 illustrates one exemplary configuration of octet 1of the Extended service request cause information element.

TABLE 11 Extended service request cause value (octet 1) Bits 3 2 1 0 0 0Originating Conversational Call 0 0 1 Originating High PrioritySignalling 0 1 0 Originating Low Priority Signalling All other valuesare reserved.

In some cases, the existing Service type information element presentwithin existing Extended Service Request messages may be modified andused to identify the CS service being requested. Alternatively,additional information elements that indicate the originating service,such as “SS Code” or “LCS indicator” defined for the ServiceNotification message may be included in the message when a UA initiatesa Mobile Originating call. In another example, the CS serviceinformation may be included in the RRCConnectionRequest message (see3GPP TS 36.331) that may be used to transition the UA from idle mode toconnected mode when initiating a Mobile Originating call subject to CSfallback.

FIG. 7 shows an example block diagram of the UA 10. While a variety ofknown components of UAs 10 are depicted, in an embodiment a subset ofthe listed components and/or additional components not listed may beincluded in the UA 10. The UA 10 includes a processor such as a digitalsignal processor (DSP) 802, and a memory 804. As shown, the UA 10 mayfurther include an antenna and front end unit 806, a radio frequency(RF) transceiver 808, and an analog baseband processing unit 810. Invarious configurations, UA 10 may include additional, optionalcomponents as illustrated in FIG. 7. The additional components mayinclude, for example, a microphone 812, an earpiece speaker 814, aheadset port 816, an input/output interface 818, a removable memory card820, a universal serial bus (USB) port 822, a short range wirelesscommunication sub-system 824, an alert 826, a keypad 828, a liquidcrystal display (LCD), which may include a touch sensitive surface 830,an LCD controller 832, a charge-coupled device (CCD) camera 834, acamera controller 836, and a global positioning system (GPS) sensor 838.In an embodiment, the UA 10 may include another kind of display thatdoes not provide a touch sensitive screen. In an embodiment, the DSP 802may communicate directly with the memory 804 without passing through theinput/output interface 818.

The DSP 802 or some other form of controller or central processing unitoperates to control the various components of the UA 10 in accordancewith embedded software or firmware stored in memory 804 or stored inmemory contained within the DSP 802 itself. In addition to the embeddedsoftware or firmware, the DSP 802 may execute other applications storedin the memory 804 or made available via information carrier media suchas portable data storage media like the removable memory card 820 or viawired or wireless network communications. The application software maycomprise a compiled set of machine-readable instructions that configurethe DSP 802 to provide the desired functionality, or the applicationsoftware may be high-level software instructions to be processed by aninterpreter or compiler to indirectly configure the DSP 802.

The antenna and front end unit 806 may be provided to convert betweenwireless signals and electrical signals, enabling the UA 10 to send andreceive information from a cellular network or some other availablewireless communications network or from a peer UA 10. In an embodiment,the antenna and front end unit 806 may include multiple antennas tosupport beam forming and/or multiple input multiple output (MIMO)operations. As is known to those skilled in the art, MIMO operations mayprovide spatial diversity which can be used to overcome difficultchannel conditions and/or increase channel throughput. The antenna andfront end unit 806 may include antenna tuning and/or impedance matchingcomponents, RF power amplifiers, and/or low noise amplifiers.

The RF transceiver 808 provides frequency shifting, converting receivedRF signals to baseband and converting baseband transmit signals to RF.In some descriptions a radio transceiver or RF transceiver may beunderstood to include other signal processing functionality such asmodulation/demodulation, coding/decoding, interleaving/deinterleaving,spreading/despreading, inverse fast Fourier transforming (IFFT)/fastFourier transforming (FFT), cyclic prefix appending/removal, and othersignal processing functions. For the purposes of clarity, thedescription here separates the description of this signal processingfrom the RF and/or radio stage and conceptually allocates that signalprocessing to the analog baseband processing unit 810 and/or the DSP 802or other central processing unit. In some embodiments, the RFtransceiver 808, portions of the antenna and front end 806, and theanalog baseband processing unit 810 may be combined in one or moreprocessing units and/or application specific integrated circuits(ASICs). The analog baseband processing unit 810 may provide variousanalog processing of inputs and outputs, for example analog processingof inputs from the microphone 812 and the headset 816 and outputs to theearpiece 814 and the headset 816.

The DSP 802 may perform modulation/demodulation, coding/decoding,interleaving/deinterleaving, spreading/despreading, inverse fast Fouriertransforming (IFFT)/fast Fourier transforming (FFT), cyclic prefixappending/removal, and other signal processing functions associated withwireless communications. In an embodiment, for example in a codedivision multiple access (CDMA) technology application, for atransmitter function the DSP 802 may perform modulation, coding,interleaving, and spreading, and for a receiver function the DSP 802 mayperform despreading, deinterleaving, decoding, and demodulation. Inanother embodiment, for example in an orthogonal frequency divisionmultiplex access (OFDMA) technology application, for the transmitterfunction the DSP 802 may perform modulation, coding, interleaving,inverse fast Fourier transforming, and cyclic prefix appending, and fora receiver function the DSP 802 may perform cyclic prefix removal, fastFourier transforming, deinterleaving, decoding, and demodulation. Inother wireless technology applications, yet other signal processingfunctions and combinations of signal processing functions may beperformed by the DSP 802. The DSP 802 may communicate with a wirelessnetwork via the analog baseband processing unit 810.

FIG. 8 illustrates a software environment 902 that may be implemented bya processor or controller of the UA 10. The software environment 902includes operating system drivers 904 that are executed by the processoror controller of the UA 10 to provide a platform from which the rest ofthe software operates. The operating system drivers 904 provide driversfor the UA hardware with standardized interfaces that are accessible toapplication software. The operating system drivers 904 includeapplication management services (“AMS”) 906 that transfer controlbetween applications running on the UA 10. Also shown in FIG. 8 are aweb browser application 908, a media player application 910, and Javaapplets 912.

The UA 10 includes a processing component such as a DSP that is capableof executing instructions related to the actions described above. FIG. 9illustrates an example of a system 1000 including one or more of thecomponents that provides the functionality of UA 10. System 1000includes a processing component 1010 suitable for implementing one ormore embodiments disclosed herein. In addition to the processor 1010(which may be referred to as a central processor unit (CPU or DSP), thesystem 1000 might include network connectivity devices 1020, randomaccess memory (RAM) 1030, read only memory (ROM) 1040, secondary storage1050, and input/output (I/O) devices 1060. In some cases, some of thesecomponents may not be present or may be combined in various combinationswith one another or with other components not shown. Any actionsdescribed herein as being taken by the processor 1010 might be taken bythe processor 1010 alone or by the processor 1010 in conjunction withone or more components shown or not shown in the drawing.

The processor 1010 executes instructions, codes, computer programs, orscripts that it might access from the network connectivity devices 1020,RAM 1030, ROM 1040, or secondary storage 1050 (which might includevarious disk-based systems such as hard disk, floppy disk, or opticaldisk). While only one processor 1010 is shown, multiple processors maybe present. Thus, while instructions may be discussed as being executedby a processor, the instructions may be executed simultaneously,serially, or otherwise by one or multiple processors. The processor 1010may be implemented as one or more CPU chips.

The network connectivity devices 1020 may include one or moretransceiver components 1025 capable of transmitting and/or receivingdata wirelessly in the form of electromagnetic waves, such as radiofrequency signals or microwave frequency signals. The transceivercomponent 1025 might include separate receiving and transmitting unitsor a single transceiver. Information transmitted or received by thetransceiver 1025 may include data that has been processed by theprocessor 1010 or instructions that are to be executed by processor1010. Such information may be received from and outputted to a networkin the form, for example, of a computer data baseband signal or signalembodied in a carrier wave. The data may be ordered according todifferent sequences as may be desirable for either processing orgenerating the data or transmitting or receiving the data. The basebandsignal, the signal embedded in the carrier wave, or other types ofsignals currently used or hereafter developed may be referred to as thetransmission medium and may be generated according to several methodswell known to one skilled in the art.

The RAM 1030 might be used to store volatile data and perhaps to storeinstructions that are executed by the processor 1010. The ROM 1040 is anon-volatile memory device that typically has a smaller memory capacitythan the memory capacity of the secondary storage 1050. ROM 1040 mightbe used to store instructions and perhaps data that are read duringexecution of the instructions. Access to both RAM 1030 and ROM 1040 istypically faster than to secondary storage 1050.

The I/O devices 1060 may include liquid crystal displays (LCDs), touchscreen displays, keyboards, keypads, switches, dials, mice, track balls,voice recognizers, card readers, paper tape readers, printers, videomonitors, or other well-known input/output devices. Also, thetransceiver 1025 might be considered to be a component of the I/Odevices 1060 instead of or in addition to being a component of thenetwork connectivity devices 1020. Some or all of the I/O devices 1060may be substantially similar to various components depicted in thepreviously described drawing of the UA 10, such as the display 702 andthe input 704.

While several embodiments have been provided in the present disclosure,it should be understood that the disclosed systems and methods may beembodied in many other specific forms without departing from the spiritor scope of the present disclosure. The present examples are to beconsidered as illustrative and not restrictive, and the intention is notto be limited to the details given herein. For example, the variouselements or components may be combined or integrated in another systemor certain features may be omitted, or not implemented.

Also, techniques, systems, subsystems and methods described andillustrated in the various embodiments as discrete or separate may becombined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled or directly coupled orcommunicating with each other may be indirectly coupled or communicatingthrough some interface, device, or intermediate component, whetherelectrically, mechanically, or otherwise. Other examples of changes,substitutions, and alterations are ascertainable by one skilled in theart and may be made without departing from the spirit and scopedisclosed herein.

To apprise the public of the scope of this disclosure, the followingclaims are made:

The invention claimed is:
 1. A method implemented by a wireless devicefor circuit switched (CS) fallback from a first network that does notprovide CS domain service, the method comprising: receiving from thefirst network a paging message indicative of a circuit switched domainservice that does not require a traffic channel or conversationalresources on a second network that provides circuit-switched services;determining a channel type, among a plurality of channel types, based onthe circuit switched domain service indicated by the paging message; andtransmitting, to the second network, a request message for initiatingestablishment of an initial radio connection with the second network,the request message indicative of the determined channel type.
 2. Themethod of claim 1, wherein the circuit switched domain service is one ofa first category of service, the first category of service includingmobile terminated location requests or a second category of service, thesecond category of service including supplementary services.
 3. Themethod of claim 2, wherein, if the circuit switched domain service is inat least one of the first or second categories of service, thedetermined channel type, among the plurality of channel types, suitablefor the circuit switched domain service is a stand-alone dedicatedcontrol channel SDCCH.
 4. The method of claim 1, wherein, when thecircuit switched domain service is undefined, the determined channeltype, among the plurality of channel types, suitable for the circuitswitched domain service is determined to be a default channel.
 5. Themethod of claim 1, wherein determining comprises detecting at least oneof a supplementary service SS code information element, a locationservice LCS indicator element, or an LCS client identity informationelement within the paging message; and wherein when the paging messageincludes the SS code information element, the determined channel type,among the plurality of channel types, suitable for the circuit switcheddomain service is selected for a call independent supplementary service;and when the paging message includes at least one of the LCS indicatorinformation element or the LCS client identity information element, thechannel type suitable for the circuit switched domain service isselected for a mobile terminated location request.
 6. The method ofclaim 1, wherein the paging message includes a CS SERVICE NOTIFICATIONMESSAGE.
 7. The method of claim 1, wherein the paging message includesan E-UTRAN RRC protocol paging message received after a preliminarypaging procedure implemented using an S1 interface.
 8. A wireless deviceconfigured to perform circuit switched fallback from a first networkthat does not provide a circuit switched domain service, the wirelessdevice comprising: a processor, the processor being configured to:receive from the first network a paging message indicative of a circuitswitched domain service that does not require a traffic channel orconversational resources on a second network that providescircuit-switched services; determine a channel type, among a pluralityof channel types, based on the circuit switched domain service indicatedby the paging message; and transmit, to the second network, a requestmessage for initiating establishment of an initial radio connection withthe second network, the request message indicative of the determinedchannel type.
 9. The wireless device of claim 8, wherein the circuitswitched domain service is one of a first category of service, the firstcategory of service including mobile terminated location requests or asecond category of service, the second category of service includingsupplementary services.
 10. The wireless device of claim 9, wherein, ifthe circuit switched domain service is in at least one of the first orsecond categories of service, the determined channel type, among theplurality of channel types, suitable for the circuit switched domainservice is a stand-alone dedicated control channel SDCCH.
 11. Thewireless device of claim 8, wherein, when the circuit switched domainservice is undefined, the determined channel type, among the pluralityof channel types, suitable for the circuit switched domain service isdetermined to be a default channel.
 12. The wireless device of claim 8,wherein determining comprises detecting at least one of a supplementaryservice SS code information element, a location service LCS indicatorelement, or an LCS client identity information element within the pagingmessage; and wherein when the paging message includes the SS codeinformation element, the determined channel type, among the plurality ofchannel types, suitable for the circuit switched domain service isselected for a call independent supplementary service; and when thepaging message includes at least one of the LCS indicator informationelement or the LCS client identity information element, the channel typesuitable for the circuit switched domain service is selected for amobile terminated location request.
 13. The wireless device of claim 8,wherein the paging message includes a CS SERVICE NOTIFICATION MESSAGE.14. The wireless device of claim 8, wherein the paging message includesan E-UTRAN RRC protocol paging message received after a preliminarypaging procedure implemented using an S1 interface.
 15. A non-transitorycomputer readable medium storing machine readable instructions which,when executed, cause a machine to: receive from a first network, thatdoes not provide circuit switched domain service, a paging messageindicative of a circuit switched domain service that does not require atraffic channel or conversational resources on a second network thatprovides circuit-switched services; determine a channel type, among aplurality of channel types, based on the circuit switched domain serviceindicated by the paging message; and transmit, to the second network, arequest message for initiating establishment of an initial radioconnection with the second network, the request message indicative ofthe determined channel type.
 16. The non-transitory computer readablemedium of claim 15, wherein the circuit switched domain service is oneof a first category of service, the first category of service includingmobile terminated location requests or a second category of service, thesecond category of service including supplementary services.
 17. Thenon-transitory computer readable medium of claim 16, wherein, if thecircuit switched domain service is in at least one of the first orsecond categories of service, the determined channel type, among theplurality of channel types, suitable for the circuit switched domainservice is a stand-alone dedicated control channel SDCCH.
 18. Thenon-transitory computer readable medium of claim 15, wherein, when thecircuit switched domain service is undefined, the determined channeltype, among the plurality of channel types, suitable for the circuitswitched domain service is determined to be a default channel.
 19. Thenon-transitory computer readable medium of claim 15, wherein determiningcomprises detecting at least one of a supplementary service SS codeinformation element, a location service LCS indicator element, or an LCSclient identity information element within the paging message; andwherein when the paging message includes the SS code informationelement, the determined channel type, among the plurality of channeltypes, suitable for the circuit switched domain service is selected fora call independent supplementary service; and when the paging messageincludes at least one of the LCS indicator information element or theLCS client identity information element, the channel type suitable forthe circuit switched domain service is selected for a mobile terminatedlocation request.
 20. The non-transitory computer readable medium ofclaim 15, wherein the paging message includes a CS SERVICE NOTIFICATIONMESSAGE.